1. Field of the Invention
The present invention relates to an electrical connecting member for electrically connecting electrical circuit components and a manufacturing method therefor.
2. Related Background Art
As a method for obtaining electrical connecting states between electric circuit components, there are a wire bonding method and an automated bonding method using the tape carrier system which are disclosed in Japanese Patent Laid-Open Application No. 59-139636 and others, that is, the so-called TAB (Tape Automated Bonding) method.
However, not only do these methods involve high costs, but with them, the numbers of junctions are increased between the electric circuit components, and still more there is encountered a problem that it is impossible to apply them if the density of the junctions becomes high.
Also, with these methods, an overall connecting condition cannot be obtained between many of the junctions. As a result, an enormous amount of processes are required, thus creating a problem that the cost reduction is limited.
To overcome such difficulties, there is known a technique to connect electric circuit components themselves electrically using the electrical connecting members held in the insulated containers in which a plurality of conductive members are provided in an insulated state with each other.
For manufacturing an electrical connecting member such as this, there have been proposed those methods which are disclosed in Japanese Patent Laid-Open Application No. 63-222437, Japanese Patent Laid-Open Application No. 63-228726, Japanese Patent Laid-Open Application No. 63-246835, and Japanese Patent Laid-Open Application No. 2-49385, for example.
FIG. 17A and FIG. 17B are views schematically illustrating such electrical connecting members as well as the electrical connection between the electric circuit components using this member. In FIG. 17, a reference numeral 171 designates an electrical connecting member, and 172 and 173, the electric circuit components to be connected. The electrical connecting member 171 is constructed with a holding member 175 made of an electrical insulator containing a plurality of conductive members 174 made of metals or alloys in such a manner that the conductive members 174 are electrically insulated from themselves. One end portion 178 of the conductive member 174 is projected toward one of the electric circuit components 172 side while the other end portion 179 of the conductive member 174 is projected toward the other one of the electric circuit component 173 side (FIG. 17A). Then, to the junctions 176 of one of the electric circuit components 172, the one projected end portions 178 of the conductive member 174 are coupled by the thermocompression bonding or compression bonding which causes them to be deformed and alloyed while to the junctions 177 of the other one of the electric circuit component 173, the other projected end portions 179 of the conductive member 174 are coupled by the thermocompression bonding which causes them to be deformed and alloyed or compression bonding which causes them to be deformed (FIG. 17B). In this way, the corresponding junctions 176 and 177 of the electric circuit components 172 and 173 are connected.
In an electrical connecting member such as this, there are the advantages given below.
(1) The junctions of the electric circuit component can be made small by making the size of the conductive member fine, and the number of junctions can also be increased. Hence, the electric circuit components themselves can be connected with a high density. PA1 (2) Even for the electric circuit components having different thicknesses, it is possible to make the height of the electric circuit components always constant by changing the thicknesses of the electrical connecting members. Consequently, a multi-layer connection can be implemented easily and an assembly can be performed with a higher density. PA1 (3) It is possible to perform a stabilized connection by making the height of the projections of the conductive member to be coupled to the junctions of the electric circuit component even when the junctions of the electric circuit component are lower than the surface. Accordingly, the electric circuit components themselves can be connected easily even if their shapes are complicated. PA1 forming a layer of an insulating material which becomes a holding member on the face provided with the conductivity of a substrate; PA1 forming a plurality of holes on the layer of the insulating material so that a plurality of the holes with the substrate surface is exposed; PA1 etching the exposed substrate surface to form irregularities thereon; PA1 filling the aforesaid concavities and holes with a conductive material and depositing the conductive material over the aforesaid holes; and PA1 thinning the aforesaid layer of the insulating material, PA1 forming on the conductive surface of a substrate a photosensitive resin film which becomes a holding member; PA1 forming the aforesaid holding member by causing the aforesaid photosensitive resin film to be exposed and developed to form a plurality of the holes in which the aforesaid substrate surface is exposed; PA1 etching the aforesaid exposed substrate surface to form concavities; PA1 filling the aforesaid concavities and holes with a conductive material and depositing the conductive material over the aforesaid holes; and PA1 thinning the aforesaid layer of the insulating material, PA1 forming on the conductive surface of a substrate a plurality of photosensitive resin films which become a holding member; PA1 forming the aforesaid holding member by causing the aforesaid photosensitive resin film to be exposed and developed to form a plurality of the holes in which the aforesaid substrate surface is exposed; PA1 etching the aforesaid exposed substrate surface to form concavities; PA1 filling the aforesaid concavities and holes with a conductive material and depositing the conductive material over the aforesaid holes; PA1 removing the aforesaid substrate; and PA1 removing a part of the aforesaid holding member, PA1 forming on the conductive surface of a substrate a layer of an insulating material which becomes a holding member; PA1 forming a plurality of the holes in which the substrate surface is exposed by forming a plurality of holes on the aforesaid layer of the insulating material; PA1 etching the aforesaid exposed substrate surface to form concavities; PA1 filling the aforesaid concavities and holes with a conductive material and depositing the conductive material over the aforesaid holes; PA1 eluting a part of a plurality of conductive members; and PA1 removing the substrate, PA1 causing the insulating material which becomes a holding to form and hold a conductive member; and PA1 giving a softening treatment to the conductive member thus held.
For manufacturing an electrical connecting member of the kind, there has been proposed a conventional method which is disclosed in Japanese Patent Laid-Open Application No. 2-49385. Hereinafter, in conjunction with FIG. 18, this manufacturing method will be described.
FIG. 18A through FIG. 18E are cross-sectional views schematically illustrating the principal processes of the method for manufacturing an electrical connecting member. At first, a metallic sheet 181 is prepared for a substrate (FIG. 18A). Then, on this metallic sheet 181, a negative-type photosensitive resin film 182 is formed by coating polyimide resin and others to construct a holding member by spinners, and a prebaking is given at a temperature of approximately 100.degree. C. (FIG. 18B). Light is irradiated on the photosensitive resin film 182 through a photomask (not shown) having a predetermined pattern to cause it to be exposed and developed (FIG. 18C). Thus, the photosensitive resin film 182 is left on the exposed portions whereas the photosensitive film on the portions which are not exposed is removed by the development treatment to form holes 183 at the bottom of which the surface of the metallic sheet 181 is exposed. The photosensitive resin film 182 is hardened by raising the temperature from to 200.degree. to 400.degree. C. Then, the member thus processed is immersed in an etching solution and the etching is given to the exposed surface of the metallic sheet in the holes 183 to form the concavities 184 which are conductively connected to the holes 183 respectively (FIG. 18D). Subsequently, a gold plating is given with the substrate 181 as its common electrode to fill the holes 183 and concavities 184 with a conductive member 185 such as gold or the like as well as to raise it on the surface of the photosensitive resin film 182 to a predetermined height for the formation of bumps (FIG. 18E). Lastly, the metallic sheet 181 is removed by etching to produce the electrical connecting member 1 which is constructed to hold the conductive member 185 with the photosensitive resin film 182 as its holding member (FIG. 18F).
In this respect, the dimension of each part of the electrical connecting member 1 is as shown in FIG. 18F: the thickness of the photosensitive resin 182 is approximately 10 .mu.m, the diameter of the hole 183 (the column portion of the conductive member 185) is approximately 20 .mu.m, the pitch is approximately 40 .mu.m, the height of the projections of the conductive member 185 are approximately several .mu.m each for the front and rear.
In the electrical connecting member 1 thus manufactured, gold 185 constitutes the conductive member while the photosensitive region 182 constitutes the holding member. The conductive member comprises the portion 185a (hereinafter referred to as column portion 185a) and the portion 185b projecting from both faces of the holding member 182 (the end portion of the conductive member in FIG. 18, hereinafter referred to as bump portion 185b). Here, the dimension of each of the electrical connecting member 1 is that the thickness of the holding member 182 (photosensitive resin) is approximately 10 .mu.m; the diameter of the conductive member 185 (column portion 185a), approximately 15 .mu.m; pitch, approximately 40 .mu.m; and the projecting amount of the conductive member 185, several .mu.m each for the front and rear.
FIG. 19 illustrates the connecting embodiment of the electric circuit components by this electrical connecting member 1. In FIG. 19, reference numerals 194 and 195 designate the objective electric circuit components to be connected. When these components are connected using the electrical connecting member 1, the electric circuit components 194 and 195 are placed along the front and rear faces of the holding member 2 respectively, and the electrodes 40 and 50 which will be the respective connecting ends are adjusted by plain sight and then these electric circuit components 194 and 195 are pressed by an appropriate means. Consequently, the aforesaid electrodes 40 and 50 are in contact under pressure with the exposed ends of the corresponding faces of the conductive member 193, and both of them are coupled metallically, so that the electrodes 40 and 50, that is, electric circuit components 194 and 195 are electrically connected through the conductive member 193.
Now, the projected height of the conductive member 185 from the holding member 182, that is, the projected height of the so-called bump is absolutely necessary as a surplusage for the deformation work to assure the connectivity between the electric circuit components 174 and 175 and junctions 176 and 177 as shown in FIG. 17B. In the conventional method, this projected height is defined by the depth of the etching against the surface of the metallic sheet 181 as shown in FIG. 18D, that is, the depth of the concavity 184, and the height of the raised portion of the conductive member 185 in the gold plating process as shown in FIG. 18E. However, in the above-mentioned method, it takes a long time to make the etching depth of the concavity 184 deeper and the height of the raised portion of the conductive member 185 higher. Still more, as they become deeper and higher, their irregularities become greater. Moreover, they tend to spread wider in the lateral direction and there is a possibility that the adjacent bumps themselves are in contact with each other. Therefore, there is a limit for making the projected height of the bumps greater only by modifying the etching and gold plating conditions.
If the projected height of the bump is low, the surplusage for the bump deformation work becomes small when the bump is in contact with the junctions 176 and 177 and others as shown in FIG. 17A and FIG. 17B. If, for example, a passivation film is provided for the protection of the junctions 176 and 177, there is a possibility that non-contacting state is generated due to the staged difference formed between the surface of the passivation film and those of the junctions 176 and 177. In order to prevent this, it is necessary to increase the contacting pressure between the electrical connecting member 1 and electric circuit components 172 and 173. Yet there occurs a problem that it is difficult to secure a sufficient reliability only by the enhancement of the contacting pressure.
Also, here, the projected ends of the conductive members 193, and the surfaces of the electrodes 40 and 50 which are in contact with each other when they are connected are not clean in general. They are covered by oxidation contamination layers (FIG. 19). Therefore, in order to obtain a reliable connecting state between the electric circuit components 194 and 195, it is necessary to exert a sufficient pressure when the electrodes 40 and 50 are in contact under pressure with the conductive members 193 so that the oxidation contamination layers in the contacting portions are destroyed to allow their newly available surfaces to be in contact for creating the metallic coupling state. In this respect, the required pressure is 50 to 100 kgf/mm.sup.2 if both the conductive members 193 and the electrodes 40 and 50 are made of gold (Au). By this pressure, the conductive members 193 are compressed between the electrodes 40 and 50 to gain a deformation ratio of 30 to 40%. Then, in such a state, the newly available surfaces are contacted.
Nevertheless, it is difficult to equalize all over the exposed heights (at H in FIG. 20) of the conductive member 193 on the front and rear faces of the holding member 2. Generally, the conductive members 193 having various exposed heights are mixedly present on the faces of the holding member 2.
A connecting state by the electrical connecting member 1 such as this is shown in FIG. 19. In this case, the pressure exerted as described above is mostly consumed to compress the conductive members 193 which have greater exposed heights. Accordingly, sufficient deformation does not take place with respect to the conductive members 193, which have smaller exposed heights (conductive member 193 in the central portion of FIG. 19). Thus, between these conductive members and the electrodes 40 and 50, the metallic coupling state resulting from the contact of the newly available surfaces themselves cannot be obtained and part of the conductive members 193 within the adjustable region with respect to the electrodes 40 and 50 is not serviceable for connection. There is consequently a possibility that the increased electrical resistance is generated between the electrodes 40 and 50 and further, a defective conduction is invited therebetween.
On the other hand, there occurs the excessive deformations with respect to the conductive members 193 having greater exposed heights due to the intensive pressure exerted as described earlier. Accordingly, the extent of the expansion in each of the through holes 206 (FIG. 20) of the conductive members 193 becomes great and cracks due to this expansion are generated in the holding member 202 and conductive members 203 themselves, leading to the possibility that a defective conduction is also invited.
Also, if a great force is added to couple the connecting member to the circuit substrate when they are coupled, the bump portion 185b which is in contact under pressure is expanded in the lateral direction as much as approximately 1.3 times. Therefore, if there are irregularities in the height of the bump portion 185b for each of the conductive members 185, adjacent conductive members 185 are caused to be in contact with each other, which can result in a short circuit. However, it is not easy to manufacture electrical connecting members 1 having the equal height of the bump portion 185b for each of the conductive members 185. There inevitably exists a slight irregularity in the heights thereof. Therefore, it is necessary to define the coupling pitches taking this irregularity into account, hence leading to a limit in implementing the higher coupling density. There is a further room for improvement in this respect.